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Dose-focus monitor technique using a critical-dimension scanning electron microscope and its application to local variation analysis

[+] Author Affiliations
Shoji Hotta

Hitachi, Ltd., Central Research Laboratory, Kokubunji-shi, Tokyo, Japan

Timothy Brunner

IBM Semiconductor Research and Development Center, 2070 Route 52, Hopewell Junction, New York 12533

Scott Halle

IBM Research, Albany, New York

Keiichiro Hitomi

Hitachi America, Ltd., Research and Development Division, Albany, New York

Takeshi Kato

Hitachi High-Technologies Corporation, Minato-ku, Tokyo, Japan

Atsuko Yamaguchi

Hitachi, Ltd., Central Research Laboratory, Kokubunji-shi, Tokyo, Japan

J. Micro/Nanolith. MEMS MOEMS. 11(4), 043011 (Dec 11, 2012). doi:10.1117/1.JMM.11.4.043011
History: Received September 9, 2012; Revised October 29, 2012; Accepted November 13, 2012
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Abstract.  A dose-focus monitoring technique using a critical-dimension scanning electron microscope (CD-SEM) is studied for applications on product wafers. Our technique uses two target structures: one is a dense grating structure for dose determination, and the other is a relatively isolated line grating for focus determination. These targets are less than 6 μm, and they can be inserted across a product chip to monitor dose and focus variation in a chip. Monitoring precision is estimated to be on the order of 1% for dose and 10 nm for focus, and the technique can be applied to dose and focus monitoring on product wafers. The developed technique is used to analyze spatial correlation in dose and focus over a wide range of distances, using a mask with a multitude of these targets. The variation (3σ) of dose and focus difference between two monitor targets is examined for various separation distances, and the variation of focus difference increases from 10 to 25 nm as the separation distance increases from 20μm to 10mm. The variation of 10 nm observed at the shortest distance reflects focus monitoring precision, and focus variation sources such as wafer thickness variation come into play at longer distances.

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© 2012 Society of Photo-Optical Instrumentation Engineers

Citation

Shoji Hotta ; Timothy Brunner ; Scott Halle ; Keiichiro Hitomi ; Takeshi Kato, et al.
"Dose-focus monitor technique using a critical-dimension scanning electron microscope and its application to local variation analysis", J. Micro/Nanolith. MEMS MOEMS. 11(4), 043011 (Dec 11, 2012). ; http://dx.doi.org/10.1117/1.JMM.11.4.043011


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